1. Field of the Invention
The present invention relates to a circuit breaker having a cam rotation delaying function, and particularly, to a circuit breaker having a cam rotation delaying function capable of avoiding incomplete closing operation due to a rotation of a cam in a state of mechanically performing an ON/OFF operation for a load side by virtue of the rotatable cam.
2. Background of the Invention
In general, a circuit breaker is an apparatus for blocking a circuit upon occurrence of overload, short-circuit, electric leakage and electric shock by selectively switching on or off a circuit between a power source side and a load side. A construction of a circuit breaker is disclosed in the Korean Registered utility model application No. 20-0442291.
As disclosed in Korean Registered utility model application No. 20-0442291, a circuit breaker executes a charging operation for accumulating elastic energy in a closing spring, a closing operation for connecting a movable contact to a terminal by an elastic restoring force of the closing spring, and an opening operation for separating the movable contact from the terminal.
Here, the charging operation is executed as follows. That is, in a blocked state where the movable contact is separated from the terminal, a cam is rotated responsive to rotation of rotational shaft which is rotated manually or rotates automatically, and a driving lever contacted by the cam is rotated in cooperation with the rotation of the cam. Accordingly, the closing spring is compressed by the rotation of the driving lever.
The closing operation is executed as follows. Elastic energy of the closing spring is transferred to a link member of a switching mechanism such that a switching shaft connected to a third link is rotated. A leg rotated in cooperation with the rotation of the switching shaft makes the movable contact moved toward the terminal so as to come in contact with the terminal, thereby enabling current flow. During the closing operation, a connection shaft of an opening spring installed at a lower portion of the leg is moved toward the terminal, accordingly the opening spring is extended.
Here, the opening operation is executed as follows. The leg is reversely rotated by an elastic restoring force of the opening spring which has been extended during the closing operation and the movable contact is spaced from the terminal to be returned to its original location.
Here, the link member is a toggle member including a first link, a second link and a third link, and performs a toggling operation capable of enduring a repulsive load which is generated upon the closing operation of the movable contact with respect to the terminal. The first and second links are rotatably connected to each other by a first rotation pin, and the second and third links are rotatably connected to each other by a second rotation pin.
Regarding the charging operation of the thusly configured circuit breaker, when the closing spring is compressed during a closing operation, a restoring force of the closing spring is applied to a cam via a bearing pin, which is disposed at the driving lever so as to be contactable with the driving lever and the cam.
Regarding the closing operation, a restoring force of the closing spring rotates the cam in a clockwise direction based upon a cam shaft when a closing latch of a driving mechanism is rotated and accordingly the closing spring in a compressed state is extended.
Here, if a force of the closing spring is set greater than a force required for returning the cam to its original location, a force applied to the cam during the closing operation becomes greater accordingly and a rotational force of the cam in the clockwise direction becomes excessive. As a result, upon rotating back to its original location, the cam is rotated over the original location in the clockwise direction, thereby being rotated up to a location interfering with a returning rotation of the driving lever.
That is, upon the closing operation, the cam may interfere with the rotation of the driving lever and a toggle pin of the link member is located above the first link to thereby suppress a complete toggle operation. Further, the returning rotation of the driving lever is suspended by the cam, and accordingly a stopping pin of the driving lever cannot be moved up to a second support shaft, which is disposed at a lower side of the driving lever for supporting the stopping pin, resulting in disabling the closing spring to be extended to its original state.
Consequently, the related art circuit breaker has a problem in that the cam may be rotated up to an excessive location by a preset tensile force of the closing spring, thereby having the chance of being operated in an unstable state.